Family: Rosaceae

Rubus fruticosus (blackberry) is a thorny shrub known for its edible dark berries and dense, bramble-like growth. Native to Europe, it has become invasive in many parts of the world, where it can form impenetrable thickets that crowd out native vegetation and disrupt natural ecosystems. The plant produces clusters of white to pinkish flowers, followed by sweet, dark purple to black fruits that attract wildlife and people alike. Its vigorous growth, thorny stems, and ability to root from stems make it a challenging species to manage once established.

To date, Rubus fruticosus is not known to be established in the Hawaiian Islands. While other blackberry species have naturalized in the islands, this particular species has not been documented in the wild. Gardeners and land managers are encouraged to be cautious with cultivation and avoid planting it, as blackberries in general can spread rapidly and have significant ecological impacts if they escape cultivation. Preventative measures and early reporting are key to keeping Hawaii free of this potentially invasive species.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Widely naturalized in regions with temperate climates
  
• An agricultural weed, causing serious economic losses
  
• An environmental weed, impacting native ecosystems
  
• Several Rubus species are highly invasive
  
• Prickly and thorny
  
• Potentially allelopathic
  
• Biomass (dead canes) increases fire risk
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Scrambling and able to climb over and potentially smother other vegetation
  
• Forms dense, impenetrable thickets
  
• Produces viable seed both sexually and apomictically
  
• Hybridizes with other Rubus species
  
• Able to spread vegetatively
  
• Seeds dispersed by birds, frugivorous animals, water and intentionally by people
  
• Prolific seed production (potentially 1000s per square meter)
  
• Able to coppice and resprout after cutting and fires

Low Risk Traits:

• Seeds require cold stratification, and as a temperate species, may only be a threat at higher elevations in tropical and subtropical islands
  
• Edible fruit
  
• Palatable to goats and deer
  
• Herbicides may provide effective control